Cyanogenic glucosides were quantified in different organs of oil flax (Linum usitatissimum cv LCSD 199) plants at different stages of development. Monoglucosides (linamarin and lotaustralin) and diglucosides (linustatin and neolinustatin) appeared in developing embryos soon after anthesis, but mature seeds accumulated only diglucosides. Monoglucosides appeared again in germinating seeds and, in young seedlings, they were the only class of cyanogens. High levels of linamarin and lotaustralin were found in leaves throughout the vegetation period, but the highest amounts were in flowers. In contrast, these glucosides occurred in relatively small amounts in roots and in stems. The possible physiological roles of the changes are discussed.